Mental ray daylight systems are popular with Autodesk 3ds Max users because it is a single click source of light. However, without proper configuration, the RPCs can look to dark or to bright, or just not match the coloration of the rest of the scene. In an effort to reduce some of the difficulty users experience I wanted to provide some settings I use to get good results.

First, we will take a look at a rendering created with the default settings and a mental ray daylight system. Looks pretty dull. Definitely not what we would expect to see in daylight. The color is poorly saturated (caused by the gamma settings), the RPCs are dark (caused by the exposure settings) and the RPCs don’t have the correct contrast (caused by the physical scale of the scene).

With only 3 changes we are going to make this look completely different without greatly affecting the red, blue and green spheres (representative of other objects in the scene). This will affect the way that the mental ray sky looks, but it should look more realistic in a scene lit by daylight.

Change 1
First, let’s change the Gamma to 2.2. Gamma for RPC objects is accessed by clicking on the Utilities panel and then selecting More followed by RPC Mass Utility. Instructions for this are available here. The results will look like this. Not an overly noticeable change, but the color is now more saturated.

Change 2
Next, we need to brighten the RPCs. To do this, go into the Exposure Settings (Rendering–>Exposure Control) and change the Exposure Value for the mr Photographic Exposure Control to 14. This will make a great difference in the brightness of the RPCs.

Change 3
Next we need to change the the Physical Scale (located just underneath the Exposure controls to Unitless and 90,000. This makes a world of difference.

Lighting is the key to realism in 3D rendering. There are many different variables that can be modified to achieve different results, but I have found that when users are experiencing difficulty changing these few settings usually yields much better results. If you ever have difficulty with anything RPC related, ArchVision’s Customer Service is just a click away at support.archvision.com.

Many users have noted unexpected results when using the RPC Environment with a Mental Ray Daylight System. This is primarily because of the way that Mental Ray blends colors. There is a large sky texture that is some shade of blue and a ground plane that is brown or green. The effect of the blending of these two becomes a murky brown/green where blue should be. Through a little trial and error I have created a settings formula that works nicely with most scene configurations.

When the RPC Environment is added to a scene with a Mental Ray Daylight System it will render something like this:

RPC Environment with Mental Ray - Default Settings

This looks nothing at all like the rendering results with the scanline rendering. I will show you how to fix this.

We will start by changing the Physical Scale values under the Environment and Effects panel. I have changed from Physical Units to Unitless and changed the value from 1500 to 90,000.

Physical Scale set to Unitless 90,000

This gives us the following results:

Rendering results with new Physical Scale

There isn’t much change shown, but when we make the next modification it will be apparent. Go into the RPC Mass Edit Dialog and change the Self-Illumination value from 0 to 55.

Mass Edit Dialog Self Illumination

Now the RPC Environment’s color will render much better.

Rendering with New Values Applied

Finally the sky looks more blue than green. To make it look even better I will brighten the scene by boosting the exposure value from 15 to 14 (lower values increase brightness). This will give us a rendering that looks like this:

Rendering with New Exposure Control Value

Utilize the exposure controls to tweak your rendering even further.
I hope this tip helps and good luck with your next rendering.

Welcome to blog.archvision.com

Welcome. ArchVision is the creator of RPC ("Rich Photorealistic Content") People, Trees, Automobiles and Objects and tools to place, edit, create and manage RPC Content in over 16 industry applications.

Our blog shares points of view and insights about the things that inspire and drive us. Our contributors - - employees, owners, partners and customers - - have a diverse range of interests and backgrounds. They work hard, play hard and are here to share their experiences, thoughts and ideas with you!